Ramjet fuel regulator



July 10, 1956 L. s. BILLMAN 2,753,686

RAMJET FUEL REGULATOR Filed May 1e, 1951 BUR/Vf@ P/QESSUR United States Patent O RAMJET FUEL REGULATOR Louis S. Billman, Glastonbury, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application May 16, 1951, Serial No. 226,579

12 Claims. (Cl. 60-39.28)

This invention relates to fuel controls for burners and more particularly to a fuel control system for maintaining burner pressure and efliciency at a maximum.

It is an object of this invention to provide a fuel regulator system for burners or ramjet units whereby the burner pressure is maintained substantially at a maximum.

Another object of this invention is to provide a fuel regulating system comprising a pair of burners whereby fuel to the burners is fed at predetermined dilferent rates and .the pressure differential resulting in the burners through the range of fuel-air ratio values is utilized to control the main fuel rate flow.

A still further object of this invention is to provide a fuel control system of the type described wherein the burners can be set to operate at any desired slope of the pressure versus fuel-air ratio curve of the burners or at a desired fuel-air ratio regardless of variations of mass air ilow through the burners.

These and other objects will become readily apparent from the following detailed description of the drawing in which:

Fig. l is a positive partially cut away View of a ramjet unit.

Fig. 2 is a curve illustrating the relationship between burner pressure and fuel-air ratio.

Fig. 3 is a curve illustrating the relationship between the pressure differential between the burner spaces and the fuel-air ratio; and

Fig. 4 is a simpliiied partially schematic illustration of the fuel regulator.

Referring to Fig. l, a ramjet unit is generally indicated at 10 which is divided into two complementary spaces A and B into which fuel may be injected and burned to develop thrust. An inner central body 12 may be provided so as to carry fuel and the regulating mechanism to be described.

According to this invention, in order to obtain for example maximum burner pressure and maximum thrust, the ramjet unit is divided into two combustion spaces and fuel is fed to each of the spaces but at a slightly different rate. As a result, there will be a slight differential of pressure between the burner spaces. By example then, and referring to Fig. 2, and assuming that burner section A is receiving fuel at some xed larger percentage (for example than the burner for space B, then the pressure in the burner for space A will be somewhat greater than that in the burner for space B, as shown for example by condition 1 on the curve in Fig. 2. On the lean side of the pressure fuel rate curve, as shown by conditions l and 2, the pressure differential bet-Ween burners for spaces A and B may be represented by points l and 2 on the curve shown in Fig. 3. Hence, as the fuel-rate ratio approaches stoichiometric condition where maximum pressure is also substantially obtained, the pressure differential between burners for spaces A and B will be approximately zero. This is represented by condition 3 in Figs. 2 and 3. As the fuel rate is further increased, condition 4 is obtained where the burners are operated on the rich side of the curve so that in spite of the burner for space A having a greater amount of fuel it will have a lower pressure than burner for space B. Hence, this condition is represented by negative differential as illustrated at 4 in Figs. 2 and 3.

In order to regulate fuel ow to the burners to obtain the desired conditions the differential pressure between the burners may be utilized to produce a signal to operate a servo mechanism to control fuel flow. Thus, as shown in Fig. 4, the fuel is directed through a regulator 20 and then to a supply line 22 and fuel nozzles 24 in the burner for space A and nozzles 26 in the burner for space B. The nozzles 24 may be arranged and selected so that they will discharge fuel at a fixed larger percentage relative to the nozzles 26. The arrangement of the nozzles in the ramjet unit may be as illustrated in Fig. l. The nozzles 26 for the section B may be spaced around the inner body 12. The nozzles in section A may be similarly arranged. Also a static pressure tap such as illustrated in Fig. l may be located at a convenient place on the inner body 12. A pressure tap for each of sections A and B would be provided. The pressure tap can be located almost anywhere in the unit as long as both are located in the same relative spot in each individual section. The resultant pressures in the burners for spaces A and B are fed to the regulator as illustrated with the pressure from the burner for space A being conducted into chamber 28 and the pressure from the burner for space B being con ducted internally of the bellows 36. It is then apparent that variations in the pressure differential between the burners for spaces A and B will be reflected by movements of the end wall 32 of the bellows which in turn imparts motion to one end 34 of a lever 36. The lever 36 is pivoted at 38 and extends through a seal 40 into an adjacent chamber 42. The other end of the lever 36 carries a valve seat 44 so that as the lever 36 is rocked about its pivot the ow through the valve 46 will be varied.

The Valve 46 operates as a pilot valve for the servo mechanism which uses fuel under pressure as its source of power. As the ilow through the valve 46 is varied, it will produce varied pressuresin the bellows Sil which pressure is slightly greater than the main fuel llow in the chamber 52 surrounding the bellows S0 by reason of the restriction illustrated. The end wall 56 of the bellows 50 has fixed thereto a movable valve portion S8 which in turn regulates the main fuel ilow rate leading to the burner nozzles 24 and 26.

The fuel regulator just described is in reality a closed loop servo mechanism which changes the main fuel rate until a zero pressure differential exists between the burner sections for spaces A and B. By adjusting the spring 64 which bears against the right-hand end 34 of the lever 36, the regulator can be set to operate at any desired position or slope of the pressure fuel-rate curve or at any desired fuel-air ratio. As illustrated herein, it is desirable to have the regulator set for maximum burner pressure since in a ramjet this corresponds to a maximum thrust.

It should be noted that although two substantially complementary combustion spaces have been illustrated, it maybe desirable to have one burner space of full scale size while the other burner may be merely a small pilot burner since all that is necessary is a differential in pressure between such burners to provide control.

Although only one embodiment of this invention has been illustrated and described it will be apparent that various changes and modifications may be made in the arrangement and construction of the parts without departing from the scope of this novel concept.

What it is desired to obtain by Letters Patent is:

1. In a fuel regulator system for a power plant having a pair of burners, a source of fuel, means for feeding fuel to said burners in predetermined different quantities, pressures for each burner increasing with fuel flow when the fuel-air ratio is lean and decreasing with increasing fuel flow when. the fuel-air ratio is rich, and meansl responsive to the difference in said burner pressures for varying the fuel fed to the burners.

2. in combination, a pair of burners having a mass of air flowing therethrough, a source of fuel, means for injecting fuel into said burners, including mechanism for injecting a redetermined different quantity of fuel in one of said burners proportionately to the other of said burners, said burners having different pressures therein relative to each other in response to said different fuel quantity injection, said differential varying from a positive sense to a negative sense over a range of operation in response to the fuel quantity injected in said burners, and means responsive to said differential of pressure for regulating said injecting means.

3. A combustion chamber having two combustion spaces, a fuel supply leading to said chamber, a fuel nozzle for admitting fuel in each of said spaces, one of said nozzles being arranged to admit fuel at a slower rate than the other throughout the range of fuel flow, means for measuring the pressure differences developed in said spaces, a control for the fuel flow from said supply, and means responsive to said pressure differential for operating said control.

4. A combustion chamber having two combustion spaces, a fuel supply leading to said chamber, a fuel nozzle for admitting fuel in each of said spaces, one of said nozzles being arranged to admit fuel at a slower rate than the other throughout the range of fuel flow, means for measuring the pressure dierences developed in said spaces, said pressure difference having a substantially zero value when maximum pressure is obtained in said chamber, and said maximum pressure occurring prior to maximum fuel flow whereby said pressure differences are positive at low fuel flows and negative at high fuel flows, means responsive to said pressure differentials including balance means responsive to the sign and quantity of said differentials, and a control for the fuel ow from said supply responsive to said pressure responsive means.

5. A combustion chamber according to claim 4 wherein a servo unit responds to said balance for operating said control.

6. In combination, a pair of burners having a mass of air flowing therethrough, a source of fuel, means for iujecting fuel into said burners, including mechanism for injecting a predetermined different quantity of fuel in One of said burners proportionately to the other of said burners, said burners having a differential of pressure therein relative to each other in response to said different fuel quantity injection, said differential varying from a positive sense to a negative sense over a range of operation in response to the fuel quantity injected in said burners, means responsive to said differential of pressure in positive and negative senses, servo mechanism operatively connected to said differential pressure responsive means, and valve means controlled by said servo mechanism for regulating the flow of fuel to said injecting means.

7. In a fuel regulating system for a combustion chamber having two combustion spaces, a source of fuel under pressure, means for injecting fuel into said spaces at predetermined different rates over a range of operation whereby the pressures in said spaces are proportionally different, sensing means operatively connected to said spaces and responsive to the difference in said pressures, a main fuel control valve regulating the quantity of flow from said source to said injecting means including an operating member therefor, a servo mechanism for operating said member including a source of power therefor, and means for controlling the power delivered to Said mechanism including operative connections to said sensing means.

8. In a fuel regulating system for a burner having at least two combustion spaces, means for inducting a combustion supporting fluid into said burner, a source of fuel under pressure, meansfor conducting fuel from said source for injection into said burner, means for injecting fuel into said spaces at relatively predetermined different rates for burning therein, means for sensing the differences in pressure in said spaces over the range of flow, means responsive to said sensing means for creating a controlling signal having positive and negative values commensurate with said differences in pressure, a main fuel valve, and means responsive to said signal for moving said valve in fuel increasing and decreasing directions commensurate with the value and sign of said signal.

9. In a fuel regulating system according to claim 8 wherein said signal controls a pilot valve and said main fuel valve is moved by a servo mechanism controlled by said pilot valve.

l0. In a fuel regulating system according to claim 8 wherein a bias is provided for said signal producing means for selecting the relative point of desired burner operation along the curve of fuel flow versus burner pressure.

11. In a fuel regulating system for a burner having a plurality of combustion spaces, means for inducting a combustion supporting fluid into said burner, a source of fuel under pressure, means for conducting fuel from said source for injection into said burner, means for injecting fuel into one of said spaces at a relatively different rate than to another of said spaces, means for sensing the resultant differences in pressure in said one and other spaces over the range of flow, means responsive to said sensing means for creating a controlling signal having positive and negative values commensurate with said differences in pressure, a main fuel valve for said burner, and means responsive to said signal for moving said valve in fuel increasing and decreasing directions commensurate with the value and sign of said signal.

12. In a ramjet comprising at least two separate combustion units, each of said units comprising an air inlet and a burner, a fuel supply leading to each of said units, means for admitting fuel into said units whereby fuel is admitted at a slower rate in one unit relative to the other unit throughout the range of fuel flow, means for measuring the pressures in said units, means for comparing said pressures for creating a signal, a control for the fuel supply, and means responsive to said signal for operating said control.

References Cited in the file of this patent UNITED STATES PATENTS 

